Adds `go vet` to the test procedures in both the local `Taskfile.yml` and the GitHub Actions workflow.
Also includes the following changes:
- Refactors the `trix` CLI to use the `cobra` library to improve testability.
- Adds comprehensive tests for the `trix` CLI, achieving 100% test coverage.
- Fixes a closure bug in the sigil command creation loop.
- Refactors the CLI to use Cobra's I/O writers, making the output testable.
